In chair constructions, it is highly desirable that the chair arms or arm rests be adjustable to suit the physical characteristics of different persons who may use any given chair. Usually, the chair arms, or arm rests mounted on chair arms, are moveable vertically or laterally. Sometimes , such as in dental chairs, it is also desirable to have the arm rests swing sideways or vertically out of the way to facilitate entry and exit from the chairs.
In recent times, with so much time being spent typing on keyboards at computer terminals and the like, a lot of concern has arisen about the need to properly support a person's forearms or wrists during such activities. One proposal for addressing this concern is illustrated in U.S. Pat. No. 5,380,065 issued to Daniel F. Rohrer. This patent shows the use of a mechanical linkage to have the padded portion of the arm rest swing in a horizontal plane to get the desired position adjustment. Another proposal is shown in U.S. Pat. No. 5,393,124 issued to Gary K. Neil wherein a padded portion of an arm rest swings inwardly about a vertical axis. A difficulty with these and other prior art approaches to the problem is that there is no solid locking mechanism to hold the moveable arm rest portions in position. Either a friction or pressure mechanism, such as in the Rohrer patent, or a ball detent type mechanism, such as in the Neil patent, is used, and these are unsatisfactory because they do not have enough holding power to prevent the arm rests from moving inadvertently. In fact, these prior art devices can actually be dangerous, because persons usually lean heavily on the arm rests when getting into and out of chairs, and if the arm rests move unexpectedly, this could cause the person to fall resulting in an injury.
In the present invention, a movable arm rest portion is positively locked in position by having at least one locking pin securely located in a transverse recess, so that downward or sideways pressure on the arm rest cannot cause it to move unexpectedly.